Thursday, March 30, 2006

In 1986 during the prehistory of Hardness vs. Randomness, Sipser
showed
that if time does not have nontrivial space simulations one can
derandomize. Given a (later-proved) assumption about extractor constructions

If there is a constant c such that DTIME(2cn) is not
contained in DSPACE(2.99cn) then P=RP.

Later results used hardness against nonuniform circuits to derandomize
complexity classes. For example Impagliazzo and Wigderson show

If E does not have circuits of size
2o(n) then P=BPP.

where E=DTIME(2O(n)).

I recently discovered that Peter Bro Miltersen in his derandomization
survey (page 56) notes that you can use a uniform assumption, a
weaker version of Sipser's assumption.

If E is not contained is DSPACE(2o(n))
then E does not have circuits of size
2o(n) and thus P=BPP.

Miltersen's proof works by searching all circuits, using the local
checkability of E to verify the correctness of the circuit.

You can even assume the circuits have access to QBF or
Σ2p gates, the later an assumption we
needed in a recent
paper.
Saying E is not contained in subexponential space is so much
nicer than saying E does not have nonuniform subexponential-size
circuits with Σ2p gates.

Technical Note: For all of the above you need to assume the
separations at all input lengths.

Wednesday, March 29, 2006

Many of us seniors are currently choosing among PhD programs. As you
probably know, we are expected to come to a decision by April 15.

Would you mind sharing with us your advice on how an aspiring theorist
should go about making this very difficult and important decision? I
personally would find such a post very informative, and I'm certain
many others would agree.

A great question but one where I have a conflict of interest—In
my view you should all have Chicago as your first choice.

Choosing an university can be sometimes easy, sometimes hard. You may
choose a university because there's a particular faculty member that
you want to work with. That's risky, because often there's no
guarantee that the faculty member will be able to take you on as a
supervisor. As a general rule, it would be best to choose an
university with a reputation for high-quality research results. This
can be measured, well, by your opinion of different research
papers. If you look at some papers, and you find some that you think
are good, look where those authors are from. This may be difficult for
a student who has yet to begin a research career: then the advice of
faculty members at your undergraduate institution can help. I think it
is generally a good idea, although I didn't follow this advice, to
study for a graduate degree at a different school than your
undergraduate institution, because you'll get a different point of
view from the faculty, as you will meet many new potential
collaborators. In choosing a graduate school the most important thing
is that you understand what it is that you want to study.

Let me add that you should, if all possible, visit the schools you are
interested in, talk to the faculty and current students. Make sure
that you will feel comfortable in that environment, it will make for a
much more enjoyable graduate experience.

If the internet was separated into regions, how much would you lose?
How often do you visit other countries' web sites? How often do you
e-mail people in other countries? What would foreigners lose by not
being able to visit US-hosted sites, and how quickly would they be
able to recreate what they lost? What other process that we are not
normally aware of depend on a borderless internet?

As an academic an international internet has gone from being a useful
tool to a critical part of scientific progress. Yesterday alone I had
four conversations with different scientists abroad on topics like
collaborations on conference and journal papers, conference
organization and recommendation letters. Many of my co-authors live
abroad and my research would greatly suffer if I could not so easily
communicate with my colleagues. Right now I can collaborate with a
researchers in Israel as easily as one in New York.

Beyond that I download papers off of researchers homepages abroad and
they download my papers from mine. Archive and online journal sites
would have to be sychronized on different parts of a separated
internet, a difficult task to maintain. Tools like Citeseer which seek
out online papers would not function as well. And many of you would
not be reading this post—Nearly a third of the readers of this
weblog reside outside the US. And how would Luca write to us from
China about his travels there?

Speaking of Slashdot, Zeev Dvir writes

Just wanted to let you know about the current
Slashdot
poll on whether P = NP. The
comments
are hilarious.

Monday, March 27, 2006

meaning that to truly understand and appreciate computational
complexity research you need to be an active researchers yourself.

But we can't keep the attitude that computational complexity can only
be appreciated by complexity theorists or we become closed and
irrelevant. We need to sell complexity and the rest of theory to the
scientific community and the public at large.

We can learn some
lessons from great spectator sports like baseball. One cannot truly
and deeply understand baseball unless you have played the game on a
regular basis. But professional baseball knows they wouldn't exist
without their fan base. They make the game interesting to fans at
different levels of understanding, from casual fans who barely know
the basic rules of the game, to sophisticated fans who understand the
nuances of strategy.

While I will never expect to see us proving theorems in front of fifty
thousand screaming fans, we should aim to make our work understandable
and interesting to fans of theory who have different levels of knowledge
of the field.

Meanwhile Nature has a online section 2020
– Future of Computing.
An editorial
about the section
talks about an interesting relationship between science and the
computer industry.

The computer industry knows that scientists can come up with strange
ideas and requirements that may well, in time, have broader commercial
application elsewhere. This is one of the reasons why Microsoft is
engaging the scientific community with its new
Towards
2020 Science report on computers in science. That report
inspired this week's focus on computing in Nature. Microsoft is
sponsoring free web access to our articles on the subject, although,
as always, the content is exclusively Nature's responsibility.

As computing gets ever cheaper, quicker and more powerful, scientists
would do well to remember that, by being a demanding and stimulating
"user community" that engages the interest of companies such as
Microsoft, Google and Intel, they can influence the development of the
field, to everybody's benefit.

Thursday, March 23, 2006

At Dagstuhl last week Jehoshua Bruck gave a talk
giving some interesting open combinatorial problems that have
real-world applications. For example the following conjecture by
Kotzig has applications to redundant disk arrays.

For every even n, one can partition the edges of the complete graph on
n vertices into n-1 perfect matchings such that each pair of perfect
matchings forms a Hamiltonian cycle.

Kotzig's conjecture is known to hold for n=2p and n=p+1 for all primes
p and a few other special cases. The conjecture remains open for
n=16. One would think we could solve the n=16 case by brute-force
search but the search space is just too big.

This is an NP problem, one can check a partition quickly. For all
those who think they have great heuristics for NP problems, go find
the partition and then talk to me.

Bruck also asks how many gates does one need to solve parity on AND-OR
circuits with unbounded fan-in. For n-bit inputs the answer is
between 2n and 2.5n-2. The first open case comes when n=6 which
requires either 12 or 13 gates. Six does not seem like a large number
but still there are far too many circuits on 12 gates to check
quickly.

Tuesday, March 21, 2006

February Edition
After the work of Cook and Karp popularized the P versus NP question,
computer scientists immediately tried hard to prove P=NP or P≠NP. Baker,
Gill and Solovay showed that most of their approaches were doomed to
failure.

Baker, Gill and Solovay noted that complexity proofs relativized, that
is held even if all machines involved could make queries to some
"oracle," i.e., making queries to some fixed set. They
created oracles A and B such that

PA = NPA

PB ≠ NPB

If one had a relativizable proof that P ≠ NP then the proof would
also show PA ≠ NPA, contradicting their
theorem. Baker et. al. give a few more relativization results and we've seen
hundreds more since.
The paper gives very little about the
philosophical implications of their results. For a short while some researchers
thought that these results could lead to true independence of the P
versus NP question, but this thinking was quickly abandoned and later
we have seen some theorems that do not relativize, particularly in the
area of interactive proof systems.
Relativization results do help us understand what theorems to pursue,
what techniques cannot solve our questions. Nearly all the techniques
we know for time classes, outside of the algebraic techniques used
for interactive proofs, do relativize. Only a very few of the
known relativization results later had proofs in the
opposite direction.
For more read my 1994 survey The Role of Relativization in Complexity Theory.

Monday, March 20, 2006

Because the state recently banned nearly all
abortions, there is a call to boycott
South Dakota, coincidentally where my family vacationed
last summer.

Suppose there was an interesting conference being held in South
Dakota. Would you go? There is some precedence—I knew some computer
scientists who refused to attend meetings in South Carolina a few
years ago when they flew the Confederate flag over their State House.

By avoiding the conference you are mostly hurting the researchers in
that state, who likely do not share the government's viewpoints and
cannot easily move. Many scientists worldwide don't like
much of current US foreign policy but I would hope they wouldn't avoid
American conferences for that reason.

Sunday, March 19, 2006

Alex Lopez-Ortiz points out that this month's SIGMOD Record has an
interview with Moshe Vardi from Rice
University that touches on several topics of interest to the readers
of this weblog. Lopez-Ortiz picked out some highlights of Vardi's
views.

On relevance of work and best-paper awards:

We now have interesting tools to evaluate the success of work in
the long term. Things like Citeseer and Google Scholar suddenly give us
a view that we could not have had before. One thing that we discovered
from these tools is that we are actually very poor in predicting the
long term impact of work. There is very little correlation, for example,
between the best paper awards that we give and the test-of-time awards
that we give. Sometimes, miraculously, we have the same paper win the
best paper and the test-of-time awards. But that is the exception rather
than the rule. So I think people should focus on just doing the best
work they can.

On highly selective conferences and low acceptance rates:

I think the low acceptance rate is a terrible problem. I think
that the idea that we are raising the quality is nonsense. I think that
actually the quality goes down. I think we are very good at selecting
about one third to one fourth of the papers; we do a pretty good job
there. As we become more selective, the program committee gets larger,
the whole discussion gets more balkanized, and the whole process gets
more random. Nobody gets a global view.…Conferences are not
scalable. They work nicely with up to roughly 300 submissions and a
certain size of program committee. When you try to scale it up, very
good papers get lost. It becomes more political. I think we are being
held back by our own success.

On conference publication vs journal publication (Here I did some
serious cut and pasting—Alex):

We are very unique among all the sciences in how we go about
publication. We have these selective conferences. (People have stopped
calling them refereed conferences. They are not really refereed. You
don't get good referee reports.) Our conferences worked well in the
world we used to inhabit…I think we had a model that worked
successfully for about 30 years, but now we see cracks in the
foundations…I don't have a good solution to this problem. We
don't even have a good forum in which to discuss the problem…
We ought to rethink how we do it. Right now, people try to fix things
incrementally by having a larger conference with a bigger program
committee, a two-level PC, a three-level PC. Maybe we need to rethink
the way we do scholarly communication in our discipline…How can
computer science go about changing its publication culture? Are there
areas that move just as fast as we do, and have journal papers and
conferences, but conferences are not the primary vehicle? I have
questions about the basic model of scholarly publications. And I find it
fascinating that it is difficult to have a conversation about this on a
big scale, and make changes on a big scale. We are very conservative. It
is interesting that computer science has been one of the slowest
disciplines to move to open access publications. Other disciplines are
way ahead of us in using online publications.

Wednesday, March 15, 2006

Last week's Numb3rs episode "Mind Games" centered on a
purported psychic causing the mathematician Charlie Eppes to exclaim
"Let's all sit down at the Ouija Board and try to solve P versus
NP once and for all."

Tuesday, March 14, 2006

This week I am at the Dagstuhl seminar Complexity of Boolean
Functions. Schloss Dagstuhl
is an isolated conference center in Southwestern Germany that hosts
weekly seminars in computer science. They have room and board at the
center and it is difficult to go anywhere from here so we are forced
to spend time with each other, a good thing for research.

Nordström gave a talk on his paper Monday. A resolution proof of
unsatisfiability of a CNF formula takes a clause containing x and
another clause with the negation of x and resolves it into a clause
containing the remaining variables of the first two clauses. A CNF
formula is unsatisfiable iff there is a resolution proof that leads to
the empty clause. In 1985, Haken showed that
there are no polynomial-length resolution proofs for all unsatisfiable
CNF formula.

The width of a proof is the size of the largest
clause produced. The space of the proof is the number of clauses one
needs to keep in memory. No immediately obvious reason that the two
should be related but in fact the space is an upper bound on the width
and conjectured to be the same up to constant factors. Nordström
disproves the conjecture by giving a family of formulas where the
width is constant but the space is not.

Monday, March 13, 2006

It happens every spring, America's favorite binary tree, the NCAA
Men's Basketball Tournament Bracket
was announced Sunday night.
This is a single elimination tournament; win and move up the tree. In
offices across America, people print and fill out these brackets
guessing the winners of each game.

How do you score a person's predictions given the final outcome of the
games? One could simply give one point for each game, other pools
double the points in each round so each round is worth a total 32
points. Or one could base the score on seeds—there are four
regions where each has 16 teams in some predetermined order of
strength. Some pools give more points to predicting an upset, like
seed 13 beating seed 4.

Is there a mathematically ideal way to score the predictions in the
tournament yet simple enough for the average American office worker to
understand? Billions of dollars are wagered on the NCAA tourney, so
creating the perfect scheme can make quite a splash in the world of
office pools.

Friday, March 10, 2006

I receive several requests to comment on various papers claiming to prove P =
NP, P ≠NP, or the independence of the P versus NP question on this
weblog. I have a healthy skepticism about all such claims and simply
don't have time to carefully read and evaluate those papers. If there
is verified significant progress towards the P versus NP problem you
will read about in on this weblog (though the converse is not true).

Sometimes I get a flood of requests about a certain P versus NP
attempt, such as the upcoming Berkeley math department Workshop
on P vs NP. I don't have much to say, the workshop is not
involving any of the Berkeley theoretical computer scientists and
in the past we've seen other, sometimes famous, mathematicians who have
believed they have an approach to the P versus NP problem that in the
end don't pan out. To the organizers' credit, at least they
acknowledge they don't yet have a proof.

Wednesday, March 08, 2006

University presidents come and go but Lawrence Summers announcement
last month that he will resign as Harvard's president has and still
continues to create considerable discussion in the media. Summers was
best known in the non-Harvard academic world for his
politically-incorrect suggestion that the low representation of woman
in the sciences could be party due to biological difference between
man and woman.

Within Harvard he managed to upset the faculty in other ways and the
faculty's lack of confidence in Summers was a factor in his
resignation. Many of the opinions I see point to the faculty as
unfirable zealots unwilling to allow a reformer like Summers do his
job. For example consider the excerpt from an Op-Ed piece
in the New York Times.

It now remains to be seen whether Harvard's Faculty of Arts and
Sciences is capable of self-critique. Will its members acknowledge
their own insularity and excesses, or will they continue down the path
of smug self-congratulation and vanity? Harvard's reputation for
disinterested scholarship has been severely gored by the shadowy
manipulations of the self-serving cabal who forced Mr. Summers's
premature resignation. That so few of the ostensibly aggrieved faculty
members deigned to speak on the record to The Crimson, the student
newspaper, illustrates the cagey hypocrisy that permeates fashionable
campus leftism, which worships diversity in all things except
diversity of thought.

and this from a professor, Camille
Paglia of the University of the Arts in Philadelphia.

The University of Chicago is getting near the end of its own presidential search
as our current president Don Randel is moving on to head the Mellon
Foundation. The Search Committee is a combination of trustee members
and faculty, where the faculty members of the committee were chosen by
election from the faculty at large. If the faculty doesn't like the
new president then we will have no one to blame but ourselves.

Update 3/9: That was quick. Bob Zimmer, a mathematician, was just nominated for the University of Chicago presidency.

Tuesday, March 07, 2006

Michael Nielsen returns to blogging after
seven months since his last real post. He talks about his new Science paper
Quantum
Computation as Geometry with
Dowling, Gu and Doherty. Last year Nielsen had an
arXiv paper A
Geometric Approach to Quantum Circuit Lower Bounds where he showed
one can bound the minimal-size quantum circuit to implement a unitary
operation U by the length of the minimal geodesic between the identity
and U. The new Science paper shows the other direction, given a short
path one can find an efficient quantum circuit.

While others are also trying
geometric approaches to separate complexity classes, by having a tight
result, the minimal geodesic gives us the right bound. Nielsen also
shows that finding the minimal geodesic is as hard as solving a
lattice closest vector problem, which means this approach might not
have the constructivity requirement of Razborov-Rudich Natural
Proofs. Since quantum circuits can simulate classical circuits, one
can possibly prove classical lower bounds as well, maybe even an
attack on P versus NP?

Monday, March 06, 2006

In this month's CACM, CMU Chair Jeannette Wing wrote a neat Viewpoint
column Computational
Thinking (with related slides). In
the article she argues that many of the techniques we use to reason
about computation apply to much wider range of problems. She gives
many aspects of computational thinking such as

Computational thinking is using abstraction and decomposition when
attacking a large complex task or designing a large complex system. It
is separation of concerns. It is choosing an appropriate
representation for a problem or modeling the relevant aspects of a
problem to make it tractable. It is using invariants to describe a
system's behavior succinctly and declaratively. It is having the
confidence we can safely use, modify, and influence a large complex
system without understanding its every detail. It is modularizing
something in anticipation of multiple users or prefetching and caching
in anticipation of future use.

Wing goes out of her way to separate computational thinking from
thinking about computers.

Computational thinking is a way humans solve problems; it is not
trying to get humans to think like computers. Computers are dull and
boring; humans are clever and imaginative. We humans make computers
exciting. Equipped with computing devices, we use our cleverness to
tackle problems we would not dare take on before the age of computing
and build systems with functionality limited only by our
imaginations.

Jeannette Wing makes a strong case that computational thinking should
be as important a part of the learning experience as the three R's,
though in CACM she preaches to the choir. She suggests that computer
science professors teach a course "Ways to Think Like a Computer
Scientist." But how do we convince students they should take it?

Sunday, March 05, 2006

Thomas C. Hales talked at the recent AAAS meeting about his proof of the
Kepler conjecture. From a New Scientist item

In 1998 Hales submitted a computer-assisted proof of the Kepler
conjecture, a theorem dating back to 1611. This describes the most
efficient way to pack spheres in a box, wasting as little space as
possible. It appears the best arrangement resembles the stacks of
oranges seen in grocery stores.

Hales' proof is over 300 pages long and involves 40,000 lines of
custom computer code. When he and his colleagues sent it to the Annals
of Mathematics for publication, 12 reviewers were assigned to check the proof.
"After four years they came back to me and said they were 99%
sure that the proof was correct and they said were they exhausted from
checking the proof," Hale says.

As a result, the journal then took the unusual step of publishing the
paper without complete certification from the referees.

Should we trust such a computer-assisted proof? I have more faith in a
computer properly executing its code more than a mathematician
verifying a proof. But what should constitute a legitimate proof when
part of that proof is verified by a computer?

In most mathematical papers, we don't give formal logical proofs of
our theorems. Instead we give a detailed proof that gives all of the
necessary ideas to convince the reader that a formal proof would be
possible. But, at least with our current technology, that level of
informality will not work with computer code. So any proof using
computer verification should have a formal proof of the correctness of
the code.

This would require significant work from the author, but we are
talking about establishing mathematical truths. When the other
alternative is publishing the solutions to major open questions
without being fully refereed, what choice do we have?

Friday, March 03, 2006

My post A
Referee's Boycott generated quite a discussion in the comments,
particularly about Elsevier. Paul Beame asked about why the EATCS
still sponsors the Theoretical Computer Science through
Elsevier. Don Sannella, editor-in-chief of TCS-B (Logic, Semantics and
Theory of Programming), responded to Beame and earlier comments. Paul
sent me a response to Sannella's comments. I'm reposting Sannella's
comment followed by Beame's response.
Don Sannella's Comment

Regarding the relationship between EATCS and TCS: EATCS is in the
process of changing its statutes to say that it supports the spread of
the results of research and exchange of information through scientific
publications, without specific mention of TCS or any other
journal. This decision has already been made and approved by the
membership; the only thing holding up its implementation is the fact
that EATCS is legally a Belgian organization so revision of the
statutes involve lawyers etc. I think this is an appropriate change
(speaking also as a member of the EATCS Council); the previous
situation was simply a result of the way that EATCS and TCS grew up
together and were set up by the same people, starting at a time when
there were very few journals.

Regarding criticisms of TCS:

Copyright: There is a lot of misinformation circulating about
this issue. I have even caught one of the main advocates of open
access publishing making plainly false statements in a public talk. I
suggest that there would be more light and less heat if people would
take the trouble to find out what the actual situation is before
criticizing.
I think the main practical issue is ability of authors to publish
their work on their own websites. In this respect Elsevier's copyright
agreement is not significantly different from the ACM's, or
Springer's, unless there has been a recent change to these that I
haven't noticed. There is an explanation of this aspect of the
Elsevier copyright, by the Elsevier editor in charge of TCS, in the
Bulletin of the EATCS number 75 (Oct 2001). The EPrints
organization regards Elsevier as self-archiving-friendly
("green" status) and it reached that status before Springer
did.

Price: I know that TCS is expensive, probably the largest item in
any Computer Science library's journal subscription budget. But it is
also very large, with 12000 pages published per year. If you look at
the price per page (here are 2004 figures from the AMS for mathematics
journals which are by the way substantially different than the price
comparison given by Wim van Dam) the cost is $0.42/page which is
comparable with other journals. This doesn't take the thousands of
pages in ENTCS, which comes free with TCS, into account. The whole
issue of journal price is complicated because the primary mode of
access these days is electronic, and prices for electronic access are
negotiated on a case-by-case basis. If you discuss the issue with
Elsevier, the statistic they will give you is that the per-download
price of an article in TCS (computed by taking the total cost of
subscriptions and dividing by the total number of downloads, I think)
is considerably less than $1. According to Elsevier, this is the
figure that librarians care about, and the fact that it is a fraction
of the cost of interlibrary loan is the key point.

Open access:
The open access movement advocates journals that are free to
readers. In this model, the author is the one who ends up paying; this
fact is mentioned much less often and some people who advocate open
access don't appear to be aware of it. (I know of one new open-access
journal that is free to authors as well because the costs are covered
by a university, at least for the moment. The point is that somebody
needs to pay; running a journal is not a cost-free spare-time
activity. See "Guide to Business Planning for Launching a New
Open Access Journal" from the Open Society Institute.) There are
major opportunities for unfairness in the editorial process with
author-pays but otherwise the only problem I see is that with both
models co-existing, few authors with an article that would be accepted
by a "normal" journal will be willing to pay for publication
in an open access journal. Springer has recently offered authors the
choice of paying a fee in order to make a paper open access, or not
paying and leaving it as paid access. I hope they publish statistics
on how many authors decide to pay!

Academic Press versus
Elsevier: "Academic Press had its flaws but they were not
predatory in their pricing." Well, compare AMS's 2004 figure for
Information and Computation ($1.07/page, Elsevier-owned) with its 2001
figure ($1.92/page, Academic Press-owned).

Quality of TCS: As
editor-in-chief of TCS-B — which is admittedly probably not the
main part of interest to readers of this blog — I am responsible
for its quality. I think the quality is pretty good and
improving. Opinions on this may vary of course. At least, it is not
the case that the alleged decline in quality is because (as Paul Beame
asserts) "TCS went to a highly distributed editorial
board". The way that the TCS editorial board works has not
changed since it was founded in 1975, as far as I know. I wonder where
he gets his information. I am unhappy about the implied suggestion
that the TCS editorial board members are not exercising proper
editorial judgment.

Finally: I am not here to make excuses for Elsevier. My interest is
TCS (and EATCS) and replying to some points above that are factually
incorrect.
Paul Beame's Response

I am happy to hear about the EATCS change. Let me address the
two main points, copyright and price, as well as open access journals.

Copyright I agree that copyright is no worse at Elsevier than
at Springer (in fact Springer has gotten worse recently). Copyright
transfer is apparently not required given the following text I
received from Elsevier regarding a JCSS paper:

Recently, we sent you a Transfer of Copyright form relating to the
above-mentioned. We note that you have not yet returned a completed
form duly signed. In order to avoid any delay in publication, we ask
that you do so immediately. Attached you will find a further copy of
the form. Please return the completed and signed original of this form
by mail or fax, or a scanned copy of the signed original by e-mail.

If we do not hear from you by return, the article will carry a line in
place of the copyright line merely indicating that Elsevier published
the article.

This sounds all right BUT when I have explicitly took advantage of the
second option I noticed that when the article was published Elsevier
still explicitly claimed copyright on it!

Price Thinking about things as price per page is exactly the
problem. TCS was one of the top 2 or 3 theory journals and around
2000 pages annually until 1989 when it decided to go to bi-weekly
publication and a much larger editorial board and upped its page count
to 3500, raising its prices drastically overnight to keep the same
price per page. The average quality declined markedly at this time
as the good papers were swamped with more lower quality fare. TCS
still publishes many good papers but it is nowhere near as high
quality as it was in the 1980's when it got many of the top papers in
the field.

Moreover TCS is just one Elsevier journal. Their behavior with others
is part of the problem: In the early 90's I was deciding between
publishing in Annals of Pure and Applied Logic (Elsevier) and Journal
of Symbolic Logic (ASL). I was told that longer papers were more
appropriate for APAL and so submitted there. I made the mistake of not
checking prices: JSL was 12 issues a year, each over 300 pages, and
cost $400 or so annually. APAL had 4 issues per year, each about 250
pages, and cost more than $2000. The quality of the two was
similar.

I speak with librarians who have to purchase journals. The pricing
for electronic journals that Elsevier sets are bundled in such a way
that they feel forced to subscribe electronically to many journals
that they do not want to purchase. The comparison with
inter-library loan is absurd.

The price comparison should be with society-published journals such as the ACM and SIAM journals. These do provide the main office editorial staff that for-profit journals provide.

Open Access I agree that the long-term soundness of the open
access model is not yet fully established. (There are some things
that need to be paid for without voluntary investment beyond
refereeing and it is not yet completely clear how to do this
long-term.) However, if you want an example of an open access journal
that does not seem to suffer from the flaws you describe, consider
JAIR (the Journal of Artificial Intelligence Research) which has been
operating for more than a decade and is one of the top couple of
journals in AI.

(It may be too soon to tell about Theory of Computing
is in its infancy but it already has a very high quality of papers.)

Why is it that Elsevier regularly emphasizes the comparisons with nascent open access journals but regularly ignores comparisons with high quality society-published journals such as SIAM and ACM journals?

Thursday, March 02, 2006

What happened last
week? I got an email pointing to the awards site and suggesting
that I congratulate Omer Reingold in the weblog. I agreed and put up
the post and mentioned a few other winners as well. It wasn't until
several hours later that I discovered, via an anonymous comment on the
post, that the awards site went up by mistake. By that time the damage
had long been done so I decided to just leave the post.

Inadvertent announcements have always occurred but the Internet makes
the news travel faster and further and impossible to undo.

Wednesday, March 01, 2006

At the University of Chicago most courses on Monday-Wednesday-Friday run 50
minutes each and on Tuesday-Thursday run 80 minutes. Many other
universities have similar timings. Most professors seem to prefer the
longer classes especially for graduate courses: You only have to teach
two days a week, you don't have to recap as much and you get an extra
ten minutes a week.

I prefer the 50 minute lectures. Many theorems fit nicely into these
smaller lectures. These lectures are easier to prepare. But most
importantly I remember struggling to keep focused as a student in
those longer lectures and I don't want to subject my students to the
same.

There are variations on the theme. I took a graduate cryptography
class with Silvio Micali that went for three hours once a week. We did
have a muffin break in the middle and Silvio has the personality to
pull it off.

During my sabbatical year in Amsterdam I taught a short course that
had 90 minute lectures. The students insisted on having a break in the
middle. Most Dutch movies theaters inserted an intermission in the
middle of movies. Apparently the Dutch have an attention span no
longer than half of a soccer game. My kind of people.